In a configuration in which a body of a fuel injector is inserted into an assembling hole formed at a specified position of the internal combustion engine, it is required that no gas leaks from a fuel injection space (for example, a combustion chamber or an intake pipe) through a clearance between an inner surface of the assembling hole and an outer surface of the body.
Conventionally, an annular seal ring is disposed in the clearance. Specifically, as shown in JP-2005-155394A1 (US-2007-0272214A1), a diameter-shrink portion is formed on the body of the fuel injector, and the annular seal ring is provided on the diameter-shrink portion. Then, the body is inserted into the assembling hole.
However, in the conventional configuration, when the body is inserted into the assembling hole, the outer surface of the annular seal ring slides on the inner surface of the assembling hole along with a friction force. Due to the friction force, the annular seal ring may be pushed up and is displaced from the specified position of the diameter-shrink portion. If the body is further inserted into the assembling force, the annular seal ring is strongly rubbed between the inner surface of the assembling hole and the outer surface of the body. The annular seal ring may be damaged.